1. Field of the Invention
The present invention relates to compositions comprising a blend of selected alkyl phenol ethoxylates and selected alkyl phenol glycoxylates. The present invention also relates to the use of these compositions as surfactants in enhanced oil recovery processes.
2. Brief Description of the Prior Art
Surfactants are commonly used agents employed in a wide variety of commercial processes and products. In the field of enhanced oil recovery, both anionic and nonionic surfactants are being employed. See U.S. Pat. No. 4,371,444, which issued to McCoy and Naylor on Feb. 1, 1983 and is incorporated herein by reference in its entirety.
Surfactants used in enhanced oil recovery applications are required to have certain properties. First, they should reduce the interfacial tension values between the crude oil and the aqueous drive fluid used for recovery, thereby causing good emulsification of the crude oil in the drive fluid. Second, they should stay soluble at the high temperatures sometimes experienced in the oil-bearing rock formations. Third, they should remain stable and effective even in the presence of high ionic strength materials (e.g. monovalent ions such as Na.sup.+, Cl.sup.- and OH.sup.- and divalent ions such as Ca.sup.++ and Mg.sup.++) which may also be present during operations. Fourth, the cost of these surfactants should be low enough to justify recovery of the additional oil.
While there are surfactants that meet these requirements under certain operating conditions, there is a strong need for surfactants which are effective over wider or different ranges of operating conditions, particularly at high salinities and high temperatures.